Transcript A child with hyponatremia Constantinos J. Stefanidis

A child with hyponatremia
Constantinos J. Stefanidis
“P. & A. Kyriakou” Children's Hospital, Athens, Greece
The patient
A 12 month old boy had a surgical repair of inguinal hernia
Wt: 10 kg
s.Na: 139 mmol/L, K: 4.4 mmol/L, Cr: 0.5 mg/dl,
pH: 7.38, HCO3: 24 mmol/L, Htc: 35%
IV fluids during the 1st day after surgery:
100 ml/kg 0.22% NaCl in D5% (Na: 38 mmol/L) + K: 20 mmol/L
The patient
A 12 month old boy had a surgical repair of inguinal hernia
Wt: 10 kg
s.Na: 139 mmol/L, K: 4.4 mmol/L, Cr: 0.5 mg/dl,
pH 7.38, HCO3 24 mmol/L, Htc: 35%
IV fluids during the 1st day after surgery:
100 ml/kg 0.22% NaCl in D5% (Na: 38 mmol/L) + K: 20 mmol/L
2nd day after surgery:
Wt: 10.6 kg
s.Na: 132 mmol/L K: 4.1 mmol/L, Cr: 0.4 mg/dl, Htc: 31%
Urine
Specific gravity: 1009, Na+: 22 mmol/L, K+: 14 mmol/L
What is the problem of this patient?
s.Na: 132 mmol/L
Hyponatremia s.Na <136 mmol/L
Na and osmolality
Low Na
Low osmolality
H2O
ECF
ICF
Na and osmolality
Low Na
Low osmolality
H2O
ECF
ICF
Total body water (TBW)
Plasma
5% of Wt
ECF
ICF
40% of Wt
Interstitial
fluid
15% of Wt
Total body water and hyponatremia
Hyponatremia
Water retention
Normal Na stores
SIADH
Hyponatremia
Water retention
Na depletion
Clinical diagnosis of TBW changes
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Careful evaluation of the history (diarrhea,
vomiting, thirst, and polyuria)
Nursing records (daily weights, intake and
output)
Physical examination (Heart rate, BP, neck
veins, peripheral edema, and ascites)
Laboratory diagnosis of TBW
changes
Patients with normal or slightly expanded
extracellular fluid volume are more likely to
have:
 decreased Hct
 normal serum urea
 Urine Na > 20 mEq/L
Diagnosis?



Increased renal salt wasting.
Syndrome of inappropriate secretion of
antidiuretic hormone (SIADH).
Inappropriate fluid and sodium fluid
administration.
First patient
A 12 month old boy had a surgical repair of inguinal hernia
Wt: 10 kg
s.Na: 139 mmol/L, K: 4.4 mmol/L, Cr: 0.5 mg/dl,
pH 7.38, HCO3 24 mmol/L, Htc: 35%
IV fluids during the 1st day after surgery:
100 ml/kg 0.22% NaCl in D5% (Na: 38 mmol/L) + K: 20 mmol/L
2nd day after surgery:
Wt: 10.6 kg
s.Na: 132 mmol/L K: 4.1 mmol/L, Cr: 0.4 mg/dl, Htc: 31%
Urine
Specific gravity: 1009, Na+: 22 mmol/L, K+: 14 mmol/L
What was the ECF volume status of this
patient?

Increased

Decreased
Diagnosis?

Increased renal salt wasting?
Urine
Specific gravity: 1009 (240 mOsm/kg)
Volume: 1.7 ml/kg/hour
Na: 22 mmol/L
K: 14 mmol/L
NO
Diagnosis?

Syndrome of inappropriate secretion of
antidiuretic hormone (SIADH)?
Diagnostic criteria of SIADH
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
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Decreased extracellular fluid effective osmolality (< 270
mOsm/kg H2O)
Inappropriate urinary concentration (> 100 mOsm/kg
H2O)
Clinical euvolemia
Elevated urinary sodium concentration, with normal
salt and water intake
Absence of adrenal, thyroid, pituitary, or renal
insufficiency or diuretic use.
SIADH in children


Very rare
In children with brain and lung problems or in
oncology patients as a side effect of their
management
Diagnosis?

Syndrome of inappropriate secretion of
antidiuretic hormone (SIADH)?
NO
Diagnosis?

Inappropriate fluid and sodium fluid
administration?
IV fluids during the 1st day after surgery:
100 ml/kg 0.25% NaCl in D5%
(Na: 38 mmol/L) + K: 20 mmol/L
Water requirements
Based on energy expenditure of the average
hospitalized patient:

First 10 kg = 100 ml/kg/day
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Second 10 kg = 50 ml/kg/day
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Weight over 20 kg = 20 ml/kg/day
Holliday MA, Segar WE. Pediatrics 1957
Maintenance fluid requirements
These calculations of maintenance fluid
requirements (insensible and urinary water losses)
were based on energy expenditure,
assuming: 1 ml of water loss was associated with the
fixed consumption of 1 kilocalorie.
Holliday MA, Segar WE. Pediatrics 1957
Comparison of different methods for
calculating caloric expenditure
In infants by 14%
Holliday and Segar's weight based
Crawford's surface area method
Basal metabolic rate
Taylor, D et al. Arch Dis Child 2004;89:411
Energy expenditure in sick children
Energy expenditure in healthy children, is different in
acute disease or following surgery and is closer to the
basal metabolic rate (50–60 kcal/kg/day).
Briassoulis G, et al. Crit Care Med 2000
Verhoeven JJ, et al. Crit Care Med 1998
Coss-Bu JA, Klish WJ, et al. Am J Clin Nutr 2001
Energy expenditure and growth
Almost half of the caloric intake suggested by Holliday
and Segar is designated for growth.
In acute diseases this is not a realistic goal.
Coss-Bu JA, Klish WJ, et al. Am J Clin Nutr 2001
IWL was estimated to high.
Insensible water loss was estimated at:
27 ml/kg/day
Recent data suggest that it is half of this:
12 ml/kg/day
Urine volume was estimated too high
It was suggested that urinary water losses for healthy
children amount to 50–60 ml/kg/day
This was based on urine volumes with an "acceptable"
osmolarity between 150 and 600 mosm/l H2O.
Increased ADH and hyponatremia
This concept did not take into account the influence of
antidiuretic hormone (ADH) on urine flow rate.
When ADH is present, the renal solute load is
effectively excreted in a smaller urine volume
(approximately 25 ml/kg/day).
Water requirements
The calculations of maintenance fluids by Holliday
and Segar are overestimating maintenance
fluids.
Hyponatremia due to increased water intake
happens rarely. In almost all cases of
hyponatremia, the problem lies in an impaired
ability of the kidneys to excrete free water due to
the action of antidiuretic hormone
Development of hyponatremia
H2O
ADH
Neurological complications of acute
hyponatraemia
Children are at high risk for developing hyponatremic
encephalopathy at higher serum sodium concentrations than
adults.
Because their brain-to-skull
size ratio is higher, which
leaves less room for brain
expansion.
Playfor S. Arch Dis Child 2003
Neurologic morbidity and acute
hyponatraemia
>50 reported cases and 26 deaths, from hospital-acquired
hyponatremia in children who were receiving hypotonic fluids.
More than half of these cases underwent minor surgery.
Arieff et al, BMJ, 1992
16 previously healthy children who died or experienced
permanent neurologic damage as a result of hyponatremic
encephalopathy
Keating et al, Am J Dis Child, 1991
Tsimaratos M et al, Arch Pediatr, 1994
Eldredge EA et al, Pediatrics, 1997
Electrolyte-free water (EFW)
The solution of 5% dextrose in:

0.3 % NaCl (or N/3, Na+: 51 mmol/L)
1/3 of the volume of this solution is water
2/3 of the volume can be thought of as EFW
Goldberg M. Med Clin North Am. 1981
The EFW input of the patient was 660 ml or 66 ml/kg/day
Electrolyte-free water (EFW)
Hoorn EW, et al. Pediatrics 2004
How we should calculate water
requirements?
Total fluid loss during acutely illness or following surgery is
usually half of that suggested by Holliday and Segar
(50-60 ml/kg/day).
Do not infuse hypotonic solutions if the Na is <138 mEq/L
unless the patient is having a rapid water diuresis and you want to limit
the rise in Na.
Hoorn EW, et al. Pediatrics 2004
Do not infuse hypotonic solutions in maintenance fluids.
Moritz ML, Ayus. JC Pediatrics 2003
D Taylor and A Durward. BMJ 2004
Prediction of s.Na
Nain
Kin H2Oin
Naout Kout H2Oout
Na =
Naex + Kex
TBW
New Na =
(Na x TBW) + Balance (Na+K)
TBW + Balance of water
Edelman IS et al. J Clin Invest 1958
Mallie JP et al. Clin Nephrol 1998
TBW = 60% Wt
Prediction of s.Na
Nain
Kin H2Oin
Naout Kout H2Oout
Na =
Naex + Kex
TBW
Change of Na =
Infusate Na - Na
TBW + 1 L
Edelman IS et al. J Clin Invest 1958
Adrogue HJ, Madias NE. Intensive Care Med 1997
TBW = 60% Wt
Total body water
TBW = 60% Weight
Lean individuals: greater percentage of TBW
Fat individuals: smaller percentage of TBW
Young children: TBW = 65-70% Wt
Calculations of TBW from Wt and Ht
For Boys:
V (liters) = -1.9 + 0.46*Wt (kg) + 0.04*Ht (cm) when Ht < 132.7 cm
V = - 22 + 0.41*Wt
+ 0.21*Ht
when Ht > 132.7 cm
For Girls:
V = 0.07 + 0.51*Wt
+ 0.01*Ht
when Ht < 110.8 cm
V = -10.3 + 0.25*Wt
+ 0.15*Ht
when Ht > 110.8 cm
Cheek DB, Mellits D, Elliott D . Am J Dis Child 1966
Calculations of TBW from Wt and Ht
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Infants 0 to 3 mo (n= 71):
TBW = 0.89 x (Wt)0.83
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Children 3 mo to 13 yr (n = 167):
TBW = 0.085 x 0.95 [if female] x (Ht x Wt)0.65
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Children > 13 yr (n = 99):
TBW = 0.075 x 0.84 [if female] x (Ht x Wt)0.69
Morgenstern BZ et al, J Am Soc Nephrol 2002
Calculations from BI
Bioelectrical Impedance (BI) is a fast and
convenient method for measuring total body
water content (TBW)
Prediction of s.Na
New Na =
(Na x TBW) + Balance (Na+K)
TBW + Balance of water
Mallie JP et al. Clin Nephrol 1998
New Na = Na +
Infusate Na - Na
TBW + 1 L
Adrogue HJ, Madias NE. Intensive Care Med 1997
Prediction of s.Na
New Na = Na +
Infusate Na - Na
TBW + 1 L
Adrogue HJ, Madias NE. Intensive Care Med 1997
The effect of urine volume, Na, K.
New Na = Na +
Infusate Na - Na
TBW + 1 L
Adrogue HJ, Madias NE. Intensive Care Med 1997
The appropriate volume and
Na of infusate
Correction of Na: 131 mEq/L
Do not harm
Hippocrates (460-377 BC)
Recommendations
1. Check electrolytes daily in all children with IV fluids
2. Monitor urine output and urine Na and K
3. Hyponatremic (Na < 136) patients have nonphysiologic ADH
- caution with fluid volumes
- isotonic saline as initial fluid
4. The use of “maintenance” fluids is
inappropriate for many of today’s hospitalized
children.
Messages to take home
It is important to determine the exact cause of
hyponatremia in patients with acute cerebral disease:

dilutional in SIADH
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negative sodium balance in CSW
Inappropriate treatment and fluid restriction in patients
with CSW might sometimes result in fatal
hyponatremia and hypovolemia.